During phase 1, fathers were invited to attend sessions in half of Arms 1 and 2 villages.

During phase 1, fathers were not invited in the other half of Arms 1 and 2 villages.

Households in Arm 2 will receive a total of 16 sessions with identical content similar to Arm 1, but 4 of those sessions will replace group sessions held at the level of villages for personalized home visits, in which the CHV will visit each participant household to deliver these sessions. These home visits will cover identical material and topics as the group sessions in Arm 1 villages, but will be delivered on a personalized basis in the home of the mother and child. Personal barriers to the practices will be discussed and an active resolution strategy developed in concert with the CHV.

After the end of the 16 biweekly sessions (phase 1), we will re-randomize across the 40 intervention villages, stratified by Arms 1 and 2, and half of each of Arm 1 and Arm 2 villages will receive group booster visits every other month for the period between end-line and follow-up surveys. This will constitute Phase 2 of the study.

During phase 1's 16 biweekly sessions, in half of Arm 1 and Arm 2 villages (20 total), fathers will additionally be invited to attend the 16 sessions. Separate father-only sessions will be held for 4 of the 16 sessions. This randomization will end after phase 1.

At follow-up surveys, the study will collect the Home Observation for Measurement of the Environment (HOME)- Short Form (SF) inventory. The HOME-SF includes items grouped into two sub-scales: emotional support and cognitive stimulation. It has four parts: one for children under age three; a second for children between the ages of three and five; a third for children ages six through nine; and a fourth version for children ten and over. The total raw score for the HOME-SF is a simple summation of the recorded individual item scores and it varies by age group, as the number of individual items varies according to the age of the child. At the month 35-37/follow-up survey the HOME score ranged 0-55 with higher scores denoting better outcomes.

Child dietary diversity is measured using a 0-7 scale in which parents report the categories of foods eaten by the child in the past 24 hours following WHO recommendations for child feeding. Higher scores denote better dietary diversity.

a 10-item measure self-reported by the mother on relationship quality with her husband using a 3-point scale from "rarely" to "most days" experiencing things ranging from the husband insulting the wife to the husband helping with child care.

Daily stress will be assessed using the Daily Stress Index which measures on a 0-2 scale (never, sometimes, often) the difficult things that sometimes happen to people. This index has previously been used in Uganda, and the raw score will be aggregated over the 15 parts with a range of 0-30.

The study will measure maternal psychological well-being using the widely used Center for Epidemiologic Studies Depression Scale (CESD) with proven psychometric properties. The 20-item scale examines how individuals have felt in the previous week. The options include: 0= Rarely (0-1 days); 1= Some or a little of the time (at least 1-2 days); 2= Most of the days (3 or more days). Scoring is done as follows: zero for answers in the first option, 1 for answers in the second option, 2 for answers in the third option. The scoring of positive items is reversed. Possible range of scores is zero to 60, with the higher scores indicating the presence of more symptomatology.

The study will elicit maternal knowledge about child development through asking mothers about the ages at which they think the child would be able achieve certain developmental milestones, which are then compared with the expected ages reported in the literature.

The study will adapt and measure the scale to elicit beliefs developed by Cunha et al. (2013)with the target of eliciting parental beliefs regarding the benefits of providing children better cognitive and non-cognitive stimulation. The instrument asks parents about developmental milestones in language and socio-emotional development under different home scenarios, which are constructed using data from the Family Care Indicators.

The Self-Efficacy for Parenting Tasks Index-Toddler Scale (SEPTI-TS) is a 26-item questionnaire to assess parental self-efficacy in parents of toddlers. The Short Form of the SEPTI-TS showed a strong factor structure with four subscales of domain-specific parental self-efficacy (Nurturance, Discipline, Play, and Routine) that showed high reliability. Scores are rates from strongly disagree to strongly agree, and higher scores indicate stronger parental self-efficacy

Mixed group meetings with a limited number of individual home visits (12 group meetings + 4 home visits)

Group+Home sessions: Households in Arm 2 will receive a total of 16 sessions with identical content similar to Arm 1, but 4 of those sessions will replace group sessions held at the level of villages for personalized home visits, in which the CHV will visit each participant household to deliver these sessions. These home visits will cover identical material and topics as the group sessions in Arm 1 villages, but will be delivered on a personalized basis in the home of the mother and child. Personal barriers to the practices will be discussed and an active resolution strategy developed in concert with the CHV. Fathers not invited.

Mixed group meetings with a limited number of individual home visits (12 group meetings + 4 home visits) plus fathers invited.

Group+Home sessions: Households in Arm 2 will receive a total of 16 sessions with identical content similar to Arm 1, but 4 of those sessions will replace group sessions held at the level of villages for personalized home visits, in which the CHV will visit each participant household to deliver these sessions. These home visits will cover identical material and topics as the group sessions in Arm 1 villages, but will be delivered on a personalized basis in the home of the mother and child. Personal barriers to the practices will be discussed and an active resolution strategy developed in concert with the CHV. Fathers invited.

This arm will serve as the control group to identify the effects of a parenting intervention and the most effective mode of delivery, as well as the sustained impacts from the intervention

In one half of Arm 1 and Arm 2 villages above, after the end of the main intensive intervention, extended light-touch group booster sessions held every other month over two years between the two follow-up surveys will be held during phase 2.

In the other half of Arm 1 and Arm 2 villages, no boosters will be held during phase 2.

Total of all reporting groups

Maternal age in years. Father's age was not systematically recorded.

Sex breakdown for the children targeted by intervention at baseline. All children were enrolled alongside their mothers or other female primary caretaker. A total of 512 fathers were enrolled at baseline as well, all males.

Recruitment and eligibility for study participation centered on mothers with eligible children. A total of 512 fathers were surveyed at baseline alongside mothers and children out of 1152 mother-child dyads originally recruited into the study. Numbers analyzed for fathers therefore lower.

Race/ethnicity information for the targeted and enrolled child at baseline, mothers, and enrolled fathers at baseline. Numbers of participants at household level analyzed.

Recorded at level of targeted/enrolled child (household level).

The Bayley Scales of Infant Development 3rd edition (Bayley's III), is validated in African settings and provides measures for all dimensions of child development up to 42 months of age. The official age-standardized cognitive and receptive language scales have 0-19 range with higher values denoting better scores.

At baseline, the study will use the Family Care Indicators, a self-reported measure of parenting practices which measures the quality time spent with children in learning and playing activities for young children at home. Scores range 0-12. Higher values are considered to be better.

10 total villages had group sessions and invited fathers during Phase 1's 16 biweekly sessions

Mixed group meetings with a limited number of individual home visits (12 group meetings + 4 home visits)

Group+Home sessions: During phase 1, households in Arm 2 will receive a total of 16 sessions with identical content similar to Arm 1, but 4 of those sessions will replace group sessions held at the level of villages for personalized home visits, in which the CHV will visit each participant household to deliver these sessions. These home visits will cover identical material and topics as the group sessions in Arm 1 villages, but will be delivered on a personalized basis in the home of the mother and child. Fathers not invited. 10 villages total.

Mixed group meetings with a limited number of individual home visits (12 group meetings + 4 home visits)

Group+Home sessions: During phase 1, households in Arm 2 will receive a total of 16 sessions with identical content similar to Arm 1, but 4 of those sessions will replace group sessions held at the level of villages for personalized home visits, in which the CHV will visit each participant household to deliver these sessions. These home visits will cover identical material and topics as the group sessions in Arm 1 villages, but will be delivered on a personalized basis in the home of the mother and child. Fathers will also be invited. 10 villages total.

This arm will serve as the control group to identify the effects of a parenting intervention and the most effective mode of delivery, as well as the sustained impacts from the intervention

In one half of Arm 1 and Arm 2 villages above, after the end of the main intensive intervention, extended light-touch group booster sessions held every other month over two years between the two follow-up surveys will be held during phase 2.

Group sessions: Mother-child dyads in Arm 1 households will receive biweekly ECD sessions for a total of 16 sessions over 7 months. CHVs will record attendance at each session. To maximize participation, prior to each session the CHVs will send a short message service (SMS) mobile phone reminder of the session's topic, time and location to all participants.

Group+Home sessions: Households in Arm 2 will receive a total of 16 sessions with identical content similar to Arm 1, but 4 of those sessions will replace group sessions held at the level of villages for personalized home visits, in which the CHV will visit each participant household to deliver these sessions. These home visits will cover identical material and topics as the group sessions in Arm 1 villages, but will be delivered on a personalized basis in the home of the mother and child. Personal barriers to the practices will be discussed and an active resolution strategy developed in concert with the CHV.

In the other half of Arm 1 and Arm 2 villages, no boosters will be held

Group sessions: Mother-child dyads in Arm 1 households will receive biweekly ECD sessions for a total of 16 sessions over 7 months. CHVs will record attendance at each session. To maximize participation, prior to each session the CHVs will send a short message service (SMS) mobile phone reminder of the session's topic, time and location to all participants.

Group+Home sessions: Households in Arm 2 will receive a total of 16 sessions with identical content similar to Arm 1, but 4 of those sessions will replace group sessions held at the level of villages for personalized home visits, in which the CHV will visit each participant household to deliver these sessions. These home visits will cover identical material and topics as the group sessions in Arm 1 villages, but will be delivered on a personalized basis in the home of the mother and child. Personal barriers to the practices will be discussed and an active resolution strategy developed in concert with the CHV.

Block-design subtest of the Wechsler Preschool and Primary Scale of Intelligence - 4th Edition (WPPSI-IV) to measure cognitive non-verbal reasoning. This subtest produces an age-standardized scaled score that can range from 1 to 19, with higher scores denoting better outcomes. For expressive and receptive language we used Dholuo and Kiswahili versions of the British Picture Vocabulary Scale - III (BPVS III), which includes 168 items for use with ages 3-17 years old. Knowledge of receptive vocabulary is measured by asking the respondent to point to one of four pictures that corresponds to a word (object, person, or action) spoken by the assessor; for expressive vocabulary the assessor pointed to a picture and the child named it. Pictures were adapted to the Kenyan context previously. Raw language scale ranges 0-25 with higher values denoting better outcomes.

Analyzed those children who were successfully tracked until this Month 35-37 survey

At follow-up surveys, the study will collect the Home Observation for Measurement of the Environment (HOME)- Short Form (SF) inventory. The HOME-SF includes items grouped into two sub-scales: emotional support and cognitive stimulation. It has four parts: one for children under age three; a second for children between the ages of three and five; a third for children ages six through nine; and a fourth version for children ten and over. The total raw score for the HOME-SF is a simple summation of the recorded individual item scores and it varies by age group, as the number of individual items varies according to the age of the child. At the endline/month 11 survey the HOME scale scores ranged from 0-45, with higher scores denoting better outcomes.

Sample sizes at month 11/endline survey. Arms A and B created after this survey.

At follow-up surveys, the study will collect the Home Observation for Measurement of the Environment (HOME)- Short Form (SF) inventory. The HOME-SF includes items grouped into two sub-scales: emotional support and cognitive stimulation. It has four parts: one for children under age three; a second for children between the ages of three and five; a third for children ages six through nine; and a fourth version for children ten and over. The total raw score for the HOME-SF is a simple summation of the recorded individual item scores and it varies by age group, as the number of individual items varies according to the age of the child. At the month 35-37/follow-up survey the HOME score ranged 0-55 with higher scores denoting better outcomes.

Sample sizes at month 35-37/follow-up survey two years after end of Phase 1's 16 biweekly sessions.

child length-for-age measured in centimeters. Enumerators measured the child three times and calculated the mean; all measures were converted to length-for-age Z scores following World Health Organization (WHO) recommendations and calculated using Stata version 16's "zscore06" command that uses 2006 WHO child growth standards and adjusts for child age and sex. Mean score is 0 for reference population. A score of <-2 SD is considered stunted linear growth. Higher scores represent better outcomes.

At month 11/endline survey, child length-for-age was measured for a total of 1053 children out of 1070.

Child dietary diversity is measured using a 0-7 scale in which parents report the categories of foods eaten by the child in the past 24 hours following WHO recommendations for child feeding. Higher scores denote better dietary diversity.

Dietary diversity data collected for 1063 mother-child dyads at month 11/endline survey, and 942 dyads at two-year follow-up/month 35-37 survey. Arms A and B only analyzed at month 35-37 survey, Arms 1 & 2 only at month 11/endline survey.

The study will measure perceived social support using the Duke-University of North Carolina (UNC) Functional Social Support Questionnaire, which is a multidimensional, self-administered instrument that assesses the social support that a person perceives that he or she has. The social support is measured as 2 scales for confidant or affective support.

a 10-item measure self-reported by the mother on relationship quality with her husband using a 3-point scale from "rarely" to "most days" experiencing things ranging from the husband insulting the wife to the husband helping with child care.

Daily stress will be assessed using the Daily Stress Index which measures on a 0-2 scale (never, sometimes, often) the difficult things that sometimes happen to people. This index has previously been used in Uganda, and the raw score will be aggregated over the 15 parts with a range of 0-30.

The study will measure maternal psychological well-being using the widely used Center for Epidemiologic Studies Depression Scale (CESD) with proven psychometric properties. The 20-item scale examines how individuals have felt in the previous week. The options include: 0= Rarely (0-1 days); 1= Some or a little of the time (at least 1-2 days); 2= Most of the days (3 or more days). Scoring is done as follows: zero for answers in the first option, 1 for answers in the second option, 2 for answers in the third option. The scoring of positive items is reversed. Possible range of scores is zero to 60, with the higher scores indicating the presence of more symptomatology.

The study will elicit maternal knowledge about child development through asking mothers about the ages at which they think the child would be able achieve certain developmental milestones, which are then compared with the expected ages reported in the literature.

The study will adapt and measure the scale to elicit beliefs developed by Cunha et al. (2013)with the target of eliciting parental beliefs regarding the benefits of providing children better cognitive and non-cognitive stimulation. The instrument asks parents about developmental milestones in language and socio-emotional development under different home scenarios, which are constructed using data from the Family Care Indicators.

The Self-Efficacy for Parenting Tasks Index-Toddler Scale (SEPTI-TS) is a 26-item questionnaire to assess parental self-efficacy in parents of toddlers. The Short Form of the SEPTI-TS showed a strong factor structure with four subscales of domain-specific parental self-efficacy (Nurturance, Discipline, Play, and Routine) that showed high reliability. Scores are rates from strongly disagree to strongly agree, and higher scores indicate stronger parental self-efficacy

Group meetings only (16 total)

Group sessions: Mother-child dyads in Arm 1 households will receive biweekly ECD sessions for a total of 16 sessions over 8 months. 10 villages total. Fathers also invited.

Mixed group meetings with a limited number of individual home visits (12 group meetings + 4 home visits)

Group+Home sessions: Households in Arm 2 will receive a total of 16 sessions with identical content similar to Arm 1, but 4 of those sessions will replace group sessions held at the level of villages for personalized home visits, in which the CHV will visit each participant household to deliver these sessions. These home visits will cover identical material and topics as the group sessions in Arm 1 villages, but will be delivered on a personalized basis in the home of the mother and child. Personal barriers to the practices will be discussed and an active resolution strategy developed in concert with the CHV. 10 villages total, fathers not invited.

Mixed group meetings with a limited number of individual home visits (12 group meetings + 4 home visits)

Group+Home sessions: Households in Arm 2 will receive a total of 16 sessions with identical content similar to Arm 1, but 4 of those sessions will replace group sessions held at the level of villages for personalized home visits, in which the CHV will visit each participant household to deliver these sessions. These home visits will cover identical material and topics as the group sessions in Arm 1 villages, but will be delivered on a personalized basis in the home of the mother and child. Personal barriers to the practices will be discussed and an active resolution strategy developed in concert with the CHV. 10 villages total, fathers also invited.

This arm will serve as the control group to identify the effects of a parenting intervention and the most effective mode of delivery, as well as the sustained impacts from the intervention

In one half of Arm 1 and Arm 2 villages above, after the end of the main intensive intervention, extended light-touch group booster sessions held every other month over two years between the two follow-up surveys will be held

Group sessions: Mother-child dyads in Arm 1 households will receive biweekly ECD sessions for a total of 16 sessions over 7 months. CHVs will record attendance at each session. To maximize participation, prior to each session the CHVs will send a short message service (SMS) mobile phone reminder of the session's topic, time and location to all participants.

Group+Home sessions: Households in Arm 2 will receive a total of 16 sessions with identical content similar to Arm 1, but 4 of those sessions will replace group sessions held at the level of villages for personalized home visits, in which the CHV will visit each participant household to deliver these sessions. These home visits will cover identical material and topics as the group sessions in Arm 1 villages, but will be delivered on a personalized basis in the home of the mother and child. Personal barriers to the practices will be discussed and an active resolution strategy developed in concert with the CHV.

In the other half of Arm 1 and Arm 2 villages, no boosters will be held

Group sessions: Mother-child dyads in Arm 1 households will receive biweekly ECD sessions for a total of 16 sessions over 7 months. CHVs will record attendance at each session. To maximize participation, prior to each session the CHVs will send a short message service (SMS) mobile phone reminder of the session's topic, time and location to all participants.

Group+Home sessions: Households in Arm 2 will receive a total of 16 sessions with identical content similar to Arm 1, but 4 of those sessions will replace group sessions held at the level of villages for personalized home visits, in which the CHV will visit each participant household to deliver these sessions. These home visits will cover identical material and topics as the group sessions in Arm 1 villages, but will be delivered on a personalized basis in the home of the mother and child. Personal barriers to the practices will be discussed and an active resolution strategy developed in concert with the CHV.